Fig. 6

Endocardial electrocardiograms during mapping and ablation at the ventricular aspect of the tricuspid valve annulus. Arrow marks atrial electrocardiogram that has low amplitude and a far-field appearance, ABLD signals from distal tip of the ablation catheter, CSP-CSD signals from 10 polar diagnostic catheter inserted into the coronary sinus. Panel a shows signals during mapping of the orthodromic AVRT with an atrial electrocar-diogram that is 49 ms early compared to the reference in the CS3. Panel b shows signals during sinus rhythm after ablation at the previous site and termina-tion of the orthodromic AVRT. Panel c shows signals during mapping in sinus rhythm in a patient with clear ventricular preexcitation. The large amplitude ventricular signal is 40 ms early compared to the begin-ning of the delta wave in surface electrocardiogram tracings (I, II, V1 and aVF) and is in line with the beginning of the negative deflection in the unipolar recording from the distal tip of the ablation catheter (ABL UNI). Panel d shows signal after ablation at the previous site and termination of ventricular preexcitation.